Centrifugal concrete cleaner



Nov. 6, 1962 v. B. BENNETT 3,061,860

' CENTRIFUGAL CONCRETE CLEANER Filed Sept. 20, 1960 r 4 Sheets-Sheet l Van/A00 BEEN/v57? INVENTOR 1 BY I 1 r I I ATTORNEYS Nov. 6, 1962 v. B. BENNETT CENTRIFUGAL CONCRETE CLEANER 4 Sheets-Sheet 2 Filed Sept. 20, 1960 5B-Nrr INVENTOR ATTORNEYS.

Nov. 6, 1962 v. B. BENNETT 3,061,860

I CENTRIFUGAL CONCRETE CLEANER Filed Sept. 20, 1960 4 Sheets-Sheet 5 64- v24 64- '72.. -VRNI7HD 5,5E/VA/E7'7' INVENTOR Nov. 6, 1962 v. B. BENNETT CENTRIFUGAL CONCRETE CLEANER 4 Sheets-Sheet 4 Filed Sept. 20, i960 r I I I 5 5 7 IV: v// W/ w M 5 3 (a 5 M 4/ Il/Il/I/ VE/PNA/PD 49.5 ENM STT INVENTOR 64% BY W,

' ATTORNEYS United rates Patent Q 3,061,360 CENTRIFUGAL CONCRETE CLEANER Vernard B. Bennett, 3800 Kings Way, Sacramento 21, Calif.

Filed Sept. 20, 1960, Ser. No. 57,293 13 Claims. (Cl. 15-93) This invention relates to a centrifugal concrete cleaner for removing foreign matter from floors and pavements.

The object of this invention is to provide a centrifugal cleaner having a diversity of applications. Factory floors become covered with oil impregnated dirt. The machine of the present invention is adapted to remove the latter. The payments of highways are usually marked OE With white paint to show the trafiic lanes. It is usually desirable to remove the white paint markings, so that the pavement can be repainted either to renew the existing lane markings, or to re-mark same for a different arrangement of the traflic lanes. The machine of the present invention i likewise adapted to remove the painted markings from the highways. The pavements of highways also become pitted and rough due to vehicles with cleated treads, chiefly tractors and other farm machinery, travelling over same. The machine of the present invention is likewise adapted to smooth off the uneven surfaces of the pavements by removing the raised irregular portions of the latter.

Another object of the present invention is to provide a centrifugal concrete cleaner which operates on the chip ping or pecking principle.

A further object of the present invention is to provide a centrifugal concrete cleaner having a tooth arrange ment such that less vibration is encountered than in the machines of the prior art.

An additional object of the present invention is to e 3,061,860 Patented Nov. 6, 1962 FIG. 8 is a detail view showing one of the chipper teeth mounted in a bore in a pivotally mounted dog.

FIG. 9 is a view similar to FIG. 8, partly in section, showing the wall of the pivotally mounted dog.

FIG. 10 is a sectional view, taken on the section line 10-10 of FIG. 8 and looking in the direction of the arrows.

FIG. 11 is likewise a sectional view, taken on the section line 11-11 of FIG. 9 and looking in the direction of the arrows.

FIG. 12 is a partial side elevational view of the drum showing the dogs which mount the chipper teeth in two different positions.

Referring now to the drawings in detail and to FIGS. 1 and 2 in particular, the centrifugal cleaner according to the present invention, is here shown as mounted on an outer frame, designated generally by the reference numeral 10, and which is positioned at a fixed level above the floor or pavement. This outer frame is comprised by longitudinally positioned angle bars 11-11 and transversely positioned angle bars 12-12, both of which angle bars provide a centrifugal concrete cleaner having a tooth arrangement such that a smoother cleaner surface is achieved.

A still further object of the present invention is to provide a centrifugal concrete cleaner having a tooth arrangement such that painted markings can be simultane- FIG. 3 is a longitudinal vertical sectional view of the i centrifugal concrete cleaner, taken on the section line 3-3 of FIG. 2 and looking in the direction of the arrows.

FIG. 4 is a transverse vertical sectional view, taken on the section line 4-4 of FIG. 1 and looking in the direction of the arrows, showing in particular the arrangement of the rotary drum and the mounting of the chipper teeth.

FIG. 5 is a transverse vertical sectional view, taken on the section line 5--5 of FIG. 1 and looking in the direction of the arrows, showing the details of the elevating means for the inner frame, which carries the rotary drum and the chipper teeth.

FIG. 6 is a transverse vertical sectional view, taken on the section line 6-6 of FIG. 1 and looking in the direction of the arrows, showing the pivotal mounting for the inner frame.

FIG. 7 is a transverse vertical sectional view, taken on the section line 7-7 of FIG. 2 and looking in the direction of the arrows, showing a detail of the mounting of the inner frame.

are disposed with their bottom flanges in the horizontal plane and directed inwardly and their side flanges in the vertical plane and directed upwardly. These longitudinally positioned angle bars 11 and the transversely positioned angle bars 12 are united at their corners in any suitable manner, as by welding. Front wheels 13-13 are positioned beneath the outer frame 10 and adjacent the front end of the latter. 'Ihese front wheels 13-13 are rotatably mounted on an axle 14, which supports the outer frame 10 by vertically positioned hangers 16-16,

which latter are secured at their tops to the longitudinally positioned angle bars 11-11 of the outer frame 10 by bolts or machine screws 17. Adjacent their lower ends these hangers 16-16 carry bearings 15-15, in which the axle 14 is journaled.

At the rear and along the longitudinal center line of the outer frame 10, there is positioned a single caster 25, which has a swivel mounting. A right angle bracket 18 is mounted with the vertical flange abutting the vertical flange of the rear transversely positioned frame member 12, and is secured to the latter by suitable bolts or rivets 17, and has its bottom flange aligned with the bottom flange of this transversely positioned frame member but disposed rearwardly in the opposite direction. Bolts 19- 19 are mounted in suitable holes in the rearwardly extending flange of the bracket 18, are disposed on the opposite sides of the transverse center line of the latter, and at their lower ends are received in suitable screw threaded holes in a horizontally positioned plate 21 on the opposite sides of the transverse center line and adjacent the rear edge of the latter. Around these bolts 19-19 there are placed spacer sleeves 20-20, which abut the forwardly disposed flange of the bracket 18 at their upper ends and the horizontally positioned plate 21 at their lower ends. The swivel mounting for the caster 25 is comprised by a bifurcated bracket 24, the top of which is secured by bolts 22 to the horizontal plate 21. Between the horizontal plate 21 and the top of the bracket 24 there is placed a washer plate 23. A tongue 26 is secured in any suitable manner, as by welding, to the rearwardly extending flange of the bracket 18 along the transverse center line of the latter. At the top of the tongue 26 a cross bar 29 is secured to the latter, providing pull handles on the opposite sides of the same. A bracket 28 in the form of a loop is secured to the tongue 26 below the handles 29-29. Safety flags (not shown) may be mounted on the tongues 26 with their handles or staffs in this bracket.

An inner frame is designated generally by the reference numeral 30 and is comprised by longitudinally positioned angle bars 31-31 and transversely positioned angle bars 3,061,860 g ce 31 and transversely positioned angle bars 32-32 are respectively shorter than the longitudinally positioned angle bars 1111 and the transversely positioned angle bars 12--12 of the outer frame 10. The pairs of angle bars 31- 31 and 3232 are disposed with their top flanges in the horizontal plane and directed inwardly, and their side flanges in the vertical plane and directed downwardly. The longitudinally positioned angle bar 31 and the transversely positioned angle bars 32 are united at their corners in any suitable manner, as by welding. Additional longitudinally positioned angle bars 3333 are disposed within the inner frame and on opposite sides of the longitudinal center line of the latter. These latter angle bars likewise have their top flanges in the horizontal plane and directed inwardly and their side flanges in the vertical plane and directed downwardly, and are secured at their respective ends to the transversely positioned angle bars 32-32.

Adjacent the forward ends of the two frames the inner frame 30 is pivotally secured to the outer frame by bolts 34-34, as best shown in FIGS. 6 and 7. Washers 3535 are positioned intermediate the vertical flanges of the longitudinally disposed angle bars 31 of the inner frame 30 and the vertically disposed flanges of the longitudinally positioned angle bars 11 of the outer frame. The bolts 34'pass through aligned holes in the inner flanges, the washers 35 and the outer flanges, and carry nuts 36 at their outer ends.

At the rear end of the inner frame 30 there is mounted a vertically positioned bolt 37 in a suitable hole in the top flange of the transversely positioned frame member 32 and along the transverse center line of the latter. This bolt 37 is secured in place by having its head against the under side of the flange of the transversely positioned frame member 32 and an apertured'disc 38 surrounding the bolt and welded to the latter and to the upper side of the flange of the transversely positioned frame member. A plate 41 has a hole 40 therein, which receives the bolt 37, and nuts 3939 are mounted on the bolt 37 and abut the plate 41 on the opposite sides of the latter. At its outer end this plate 41 is cut away along an arc centered on its longitudinal center line, to form bifurcations 41a 41a. The tongue 26 is received between the bifurcations 41a41a on the plate 41. An inverted triangular gusset plate 27 is secured as by welding, along one side to the tongue 26 and along its base to the plate 41.

At the forward end of the inner frame 30 there is mounted an internal combustion engine, which is designated generally by the reference numeral 45. This engine need not be of any particular type, but the engine commonly used for driving a power lawn mower has been found satisfactory. It is comprised by the usual components, a fuel tank 46, an air born 47, a cylinder block '48, a crank case 49, a fly wheel housing 50, and a crank shaft 51. A chain sprocket 52 is mounted on the outer end of the crank shaft 51. The engine 45 is secured to the longitudinally positioned frame members 33--33 of the inner frame 30 in any suitable manner, as by bolts (not shown).

The rotary drum which mounts the dogs carrying'the chipper teeth, is shown in FIGS. 1 and 4, and is designated generally by the reference numeral 62. This drum is comprised by two circular plates 6363, which are welded to a shaft 56, after the dogs and chipper teeth have been assembled between same. The shaft is rotatably mounted in pillow block bearings 5757, which latter are secured by bolts 58 to the longitudinally disposed flanges of the frame members 3333 on the inner frame 30. At one outer end the shaft 56 carries a chain gear 54 and a chain 53 is trained over the chain sprocket 52 on the crank shaft of the internal combustion engine 45 and this chain gear. At the other outer end the shaft 56 carries a collar 59 which is secured to same by a pin 60. This collar 59 abuts the adjacent pillow block 4 bearing 57 to restrain movement of the shaft 56 to the left (FIG. 4).

The detailed construction of the rotatable drum 62, which mounts the dogs 64 carrying the chipper teeth 70, is shown in FIG. 12. While only two (2) sets of dogs 64 and chipper teeth 72 are shown on FIG. 4, it is contemplated that six (6) sets will be used, ranged 60 apart circumferentially of the parallel plates 63-63. Likewise, while only six (6) dogs 64 and the chipper teeth 72 carried thereby are shown in each set on FIG. 4, it is contemplated that a greater number ranging up to a maximum of twenty-four (24) will be used. The detailed mounting of a single dog 64 and the chipper tooth 72 carried thereby will now be described with reference to FIGS. 3 and 12, and later to FIGS. 8 to 11, inclusive. Each dog 64 has an elongated slot 65 therein, which slot receives a rod 67. This rod 67 extends through the parallel plates 63-63, being positioned along a diameter of the latter, and has a nut 68 on its outer end. Two (2) other rods 69 and 70 also extend between the parallel plates 6363, being positioned along a chord parallel to a second diameter of the plates and at an angle of approximately 40 with respect to the diameter through the rod 67. These rods 69 and 70 also carry nuts 68 at their outer ends. The dog 64 has a curved cam surface 64a thereon, which abuts the innermost rod 69 when the dog is in its uppermost idle position, and a curved lug 64b, which abuts the outermost rod 70, when the dog is in its lowermost position with the chipper tooth 72 disposed to engage the surface of the floor or pavement, as shown in FIG. 1. The action of the dog 64 in shifting between these positions will be later described.

As shown in FIGS. 8 and 10, each dog 64 has a slot 66 therein, in which the chipper tooth 72 is mounted. These chipper teeth are rectangular in cross section and A wide by thick have been found to be satisfactory dimensions. Adjacent its inner end each chipper tooth 72 has it turned reduced cylindrical section 72a, which is received within a slot 66 in the dog 64, this slot being of a diameter equal to the width, for instance A of the chipper teeth. The inner end of each chipper tooth is inserted in a slot 66 and the wall of the slot is then swaged around the inner end of the chipper tooth and the section 72a, as shown in FIGS. 9 and 11. The outer ends of the chipper teeth are beveled at 72b to provide a better penetrating edge.

The rotary drum 62 is partially enclosed at its top by a housing 73, which has a cover 74, is terraced transversely (FIG. 4) to provide an upper section 73a of reduced width and at the lower edge of its bottom section has outwardly extending flanges 7575. Bolts 76 pass through aligned holes in the flanges 7575 and the horizontal flanges of the longitudinally positioned angle bars 3333 of the inner frame 30.

In operation of the centrifugal concrete cleaner is pushed over the floor or pavement by the tongue 26 and the cross bars 29-29 on the latter. The internal combustion engine 45 drives the rotary drum 62 through the sprocket 52, chain 53 and chain gear 54. The chipper teeth 72 intermittently contact the floor or pavement and remove oil or grease from the former and either paint markings from or smooth off the latter, as may be required.

Referring now to FIG. 12, as the drum 62 revolves, let it be assumed that the dog 64 and the chipper tooth 72 are in the approximately horizontal position, in which position the cam surface 64:: rests on the innermost rod 69. As the drum 62 revolves farther, centrifugal force causes the dog 62 to move to the approximately vertical position shown. When in this position the curved lug surface 64b of the dog is resting firmly against the outermost bolt 70. The corresponding position of the chipper tooth 72 is the position it presently occupies when the edge 72b actually comes into contact with the floor or pavement. As the edge 72b of the chipper tooth makes contact with the floor or pavement, the chipper tooth 72 and the dog 64 are thrown upward and backward. This action is made possible by the lost motion action of the elongated slot 65 in the dog in co-operation with the rod 67, which is received therein. It is also the case that the lost motion action of the elongated slot 65 in the dog 64 and the rod 67 prevents breakage of the chipper teeth 72, due to the sudden impact With the floor or pavement. The chipper tooth 72 only contacts the floor or pavement a fraction of a second but, by the time the dog 64 and the chipper tooth have been thrown backward to the position where the cam surface 64b is in contact with the rod 659 and rebounds to the forward position with the lug surface 64b against the rod 70, the drum 67 has revolved sufiiciently far that the same chipper tooth is clear of the floor or pavement and will not make contact with the latter until the same phase in the next revolution. Even though, as stated, the chipper teeth 72 contact the floor or pavement only briefly, the centrifugal force urging the latter downwardly is adequate to impel the chipper teeth to perform their function.

By having six (6) units of dogs 64 and chipper teeth 72 uniformly arcuately spaced around the drum 62, less vibration is produced and the surface of the floor or pavement is scraped smoother, as one set of teeth will be constantly in contact with the floor or pavement. There is also the advantage, with the plurality of transversely aligned chipper teeth 72 in each unit, that paint markings can be removed from both the high and low spots on a concrete pavement. The latter, of course, could not be done with a single cutter of equal length to the transverse width of the plurality of chipper teeth 72 in a unit, since such a single cutter would remove the paint markings from only the high spots on a concrete pavement. Similarly, by placing twenty-four (24) chipper teeth 72 in transverse alignment in each unit, a considerable width of the floor may be cleaned or the pavement chipped, as the case may be, in a single run of the cleaner. However, the invention is not limited to any specific number of units of dogs 64 and chipper teeth 72 on the rotatable drum 62, or to any specific number of dogs 64 and chipper teeth 72 in each unit. The mounting of the dogs 64 through the elongated slots '65 in the latter receiving the rods 67 provides for ready removability of the dogs to replace broken or worn chipper teeth 72.

As stated, the inner frame 30 is pivotally mounted at its forward end on the bolts 3434. The angle of the elevation of the inner frame may be decreased by rotating the lowermost nut 39 downward on the threaded rod 37 and following with the upper nut 39; conversely, the angle of the elevation may be increased by rotating the upper nut upward on the rod 37 and following with the lower nut 39. This angle of elevation of the inner frame 30 determines the depth at which the chipper teeth 72 will scrape the floor or pavement and accordingly the amount of dirt, oil or grease they will remove from the former, or the depth at which they will remove paint markings from the surface or dress the surface of the latter. This angle is also important in that it enables the finishing of the surface in even and smooth manner, when the angle of elevation of the inner frame is increased to its maximum limit; conversely, in case it should be desired that the dressed concrete pavement have a corrugated or rough surface, the angle of elevation of the inner frame 30 is decreased accordingly. Such latter case might be a concrete ramp along which people walk and it would be desired to have it corrugated or rough surfaced to minimize the danger of slipping.

Having now fully described my invention, what I claim as new and useful and desire to secure by Letters Patent of the United States is:

1. A chipper drum for a centrifugal concrete cleaner comprised by a pair of parallel discs, means for rotating said drum, a first set of rods extending between said discs adjacent the peripheries of the latter and a second set of rods extending between said discs spaced arcuately from and radially inwardly from the first set of rods, dogs having cam surfaces thereon movable from an initial position to a position in which said cam surfaces engage the second set of rods, and chipper teeth carried by said dogs arranged to contact the surface over which the cleaner travels when the dogs are in their initial positions.

2. A chipper drum for a centrifugal concrete cleaner comprised by a pair of parallel discs, means for rotating said drum, a first set of rods extending between said discs adjacent the peripheries of the latter and a second set of rods extending between said discs spaced arcuately from and radially inwardly from the first set of rods, dogs pivotally mounted on said first set of rods and having lugs thereon adapted to engage said second set of rods, and chipper teeth carried by said dogs arranged to contact the surface over which the cleaner travels when the lugs on said dogs are in engagement with the second set of rods.

3. A chipper drum for a centrifugal concrete cleaner comprised by a pair of parallel discs, means for rotating said drum, a first set of rods extending between said discs adjacent the peripheries of the latter, a second set of rods extending between said discs spaced arcuately from and radially inwardly from the first set of rods, and a third set of rods also spaced arcuately from and radially inwardly from the first set of rods, dogs pivotally mounted on said first set of rods and having cam surfaces thereon adapted to engage said third set of rods and lugs thereon adapted to engage said second set of rods, and chipper teeth carried by said dogs arranged to contact the surface over which the cleaner travels when the lugs on said dogs are in engagement with said second set of rods.

4. A chipper drum for a centrifugal concrete cleaner comprised by a pair of parallel discs, means for rotating said drum, a first set of rods extending between said discs adjacent the peripheries of the latter and a second set of rods extending between said discs spaced arcuately from and radially inwardly from the first set of rods, dogs having elongated slots therein receiving said first set of rods, cam surfaces thereon movable from an initial position to a position in which said cam surfaces engage the second set of rods, and chipper teeth carried by said dogs arranged to contact the surface over which the cleaner travels when the dogs are in their initial position.

5. A chipper drum for a centrifugal concrete cleaner comprised by a pair of parallel discs, means for rotating said drum, a first set of rods extending between said discs adjacent the peripheries of the latter, a second set of rods extending between said discs spaced arcuately from and radially inwardly from the first set of rods, dogs having elongated slots therein receiving said first set of rods and having lugs thereon adapted to engage said second set of rods, and chipper teeth carried by said dogs arranged to contact the surface over which the cleaner travels when the lugs on said dogs are in engagement with the second set of rods.

6. A chipper drum for a centrifugal concrete cleaner comprised by a pair of parallel discs, means for rotating said drum, a first set of rods extending between said plates adjacent the peripheries of the latter, a second set of rods extending between said discs spaced arcuately from and radailly inwardly from the first set of rods, and a third set of rods also spaced arcuately from and radially inwardly of the first set of rods, dogs having elongated slots therein receiving said first set of rods and having cam surfaces therein adapted to engage said third set of rods, lugs thereon adapted to engage said second set of rods, and chipper teeth carried by said dogs arranged to contact the surface over which the cleaner travels when the lugs on said dogs are in engagement with said second set of rods.

7. A centrifugal concrete cleaner comprised by an outer frame including longitudinally positioned side bars and transversely positioned end bars secured to said side bars, wheels supporting said outer frame for movement over the surface to he cleaned, an inner frame including longitudinally positioned side bars spaced inwardly from the side bars of the outer frame and transversely positioned end bars spaced inwardly from the transversely positioned end bars of the outer frame and secured to the side bars of the inner frame, a drum rotatably mounted on the inner frame and having chipper teeth thereon adapted to contact the surface being cleaned, and means mounted on one of said frames for rotating the drum.

8. A centrifugal concrete cleaner comprised by an outer frame including longitudinally positioned side bars and transversely positioned end bars secured to said side bars, Wheels supporting said outer frame for movement over the surface to be cleaned, an inner frame including longitudinally positioned side liars spaced inwardly from the side bars of the outer frame and transversely positioned end hats spaced inwardly from the transversely positioned end bars of the outer frame and secured to the said side bars of the inner frame, a pivotal mounting at one end of the outer frame 'between the latter and the inner frame at the respective end of the latter, a drum rotatably mounted on the inner frame and having chipper teeth thereon adapted to contact the surface being cleaned, and means mounted on one of said frames for rotating the drum.

9. A centrifugal concrete cleaner comprised by an outer frame including longitudinally positioned side .hars and transversely positioned end bars secured to said side bars, wheels supporting said outer frame for movement over the surface to be cleaned, an inner frame including longitudinally positioned side bars spaced inwardly from the side bars of the outer frame and transversely positioned end bars spaced inwardly from the transversely positioned end bars of the outer frame and secured to the said side bars of the inner frame, a pivotal mounting at one end of the outer frame between the latter and the inner frame 'at the respective end of the latter, a drum rotatably mounted on the inner frame and having o'hipper teeth thereon adapted to contact the surface "being cleaned, a housing mounted on the inner frame and enclosing the drum above the top of the latter, and means mounted on one of said frame for rotating the drum.

10. A centrifugal concrete cleaner comprised by an outer frame including longitudinally positioned side bars, a first transversely positioned end bar secured to said side bars at one end of the latter, a second transversely positioned side bar having an inwardly extending flange secured to said side bars at the other end of the latter, wheels supporting said outer frame for movement over the surface to be cleaned, an inner frame including longitudinally positioned side bars spaced inwardly from the side bars of the outer frame and transversely positioned end bars spaced inwardly from the transversely positioned end bars of the outer frame and secured to the said side ears of the inner frame, a pivotal mounting at one end of the outer frame bet-ween the latter and the inner frame and at the end of the latter adjacent the first transversely positioned side bar of the outer frame for supporting the inner frame in horizontal position with the other end resting on the inwardly extending flange of the second transversely positioned side bar of the outer frame, a drum rotatably mounted on the inner frame and having chipper teeth thereon adapted to contact the surface [being cleaned, and means mounted on one of said frames for rotating the drum.

II. A centrifugal concrete cleaner comprised by an outer frame including longitudinally positioned side bars and transversely positioned end Phars secured to said side hars, wheels supporting said outer frame for movement over the surface to be cleaned, an inner frame including longitudinally positioned side b ars spaced inwardly from the side bars of the outer frame and transversely positioned end bars spaced inwardly from the transversely positioned end has of the outer frame and secured to the said side bars of the inner frame, a pivotal mounting at one end of the outer frame between the latter and the inner frame at the respective end of the latter, adjustahle means between the outer and inner frames for securing the inner frame in a selected elevated position with respect to the outer frame, a drum rotatably mounted on the inner frame and having chipper teeth thereon adapted to contact the surface being cleaned, and means mounted on one of said frames for rotating the drum.

12. A centrifugal concrete cleaner comprised by an outer frame including longitudinally positioned side bars and transversely positioned end bars secured to said side bars, wheels supporting said outer frame for movement over the surface to be cleaned, an inner frame including outer longitudinally positioned side bars spaced inwardly from the side ears of the outer frame, inner longitudinal- 1y positioned bars positioned on the opposite sides of the center line of the inner frame, and transversely positioned end bars spaced inwardly from the transversely positioned end bars of the outer frame and secured to the said side bars and the inner longitudinally positioned bars of the inner frame, a pivotal mounting at one end of the outer frame between the latter and the inner frame at the respective end of the latter, aligned bearings mounted on the inner longitudinally positioned bars of the inner frame, a shaft journalled in said 'bearings, a drum mounted on said shaft for rotation therewith and having chipper teeth thereon adapted to contact the surface being cleaned, and means mounted on one of said frames for rotating the drum. 7 7

13. A centrifugal concrete cleaner comprised by an outer frame including longitudinally positioned side bars and transversely positioned end lbars secured to said side bus, wheels supporting said outer frame for movement over the surface to be cleaned, an inner frame including longitudinally positioned side vbars spaced inwardly from the side bars of the outer frame and transversely positioned end bars spaced inwardly from the transversely positioned end bars of the outer frame and secured to the side bars of the inner frame, a pivotal mounting at 'one end of the outer frame between the latter and the inner frame at the respective end of the latter, a

drum rotatably mounted on the inner frame and having chipper teeth thereon adapted to contact the surface being cleaned, an engine mounted on the inner frame, and a drive between the engine and said drum.

References Cited in the file of this patent UNITED STATES PATENTS 2,279,922 Kraner Apr. 14, 1942 2,525,250 Westphal Oct. 10, 1950 2,734,498 Arx et al Feb. 14, 1956 2,746,127 Jacques May 22, 1956 2,784,482 Emmons Mar. 12, 1957 2,911,737 An: Nov. 10, 1959 

